Abstract
In the following driving in the general road, about 70% of all drivers are worse fuel economy than the ACC control by Performance Index for Approach and Alienation (KdB-ACC). But they will get good fuel economy in actual traffic by using KdB-ACC. Furthermore, selecting Eco-mode of KdB-ACC, they will get the good fuel economy of about 8% of averages (maximum of about 20%) to Normal-mode of KdB-ACC in actual traffic.